1. Field of the Invention
The present invention concerns methods and apparatus for performing porosimetric analysis on solid samples.
2. Description of the Prior Art
According to known techniques, porosimetric analyses are performed by a process in which a solid sample is introduced into a test vessel together with a quantity of a suitable liquid, such as mercury. The liquid is then subjected to an increasing pressure. The volumetric variations of the liquid which is due to the penetration of the same into the pores of the sample is then detected as pressure varies.
By this known process, it is possible to trace a pressure-volume mercury curve, on the basis of which, and according to a known formula, it is possible to obtain a size distribution of the sample's pores, and information on the same sample.
During this test very high pressure values (around 2000 atmospheres) are reached and it is clear that at the end of same it is necessary to lower pressure to values substantially equal to the ambient ones.
During this pressure reduction, the test liquid, in particular mercury, obviously tends to come out of some of the pores which it had penetrated during pressure increase. In particular it tends to come out of the pores which present an open configuration, while, on the contrary, it tends to remain inside pores which present an almost closed configuration. Therefore, a lowering pressure-volume mercury curve is obtained which presents, together with the pressure-volume mercury curve traced during the pressure increase phase, a hysteretic course, allowing indications on the shape of the sample pores to be obtained. However, these indications are relatively fragmentary and partial, in that they are obtained up to now in correspondence to one or more pressure values, practically only in correspondence to the point corresponding to the return to ambient values as well as to the point of maximum pressure value.